1. Field of the Invention
The present invention is broadly concerned with a method of preparing dry, concentrated salts of the stereoisomeric forms of ascorbate 2-polyphosphate (L-ascorbate and D-erythorbate), and particularly the calcium and magnesium salts thereof, in good yields and with a high proportion of contaminating inorganic species removed. More particularly, it is concerned with such a method wherein aqueous solutions of sodium and/or potassium L-ascorbate 2-polyphosphate are first treated by aqueous dilution, addition of CaCl.sub.2 or MgCl.sub.2, and pH adjustment as necessary in order to precipitate contaminating inorganic salts; the supernatant is then concentrated, and a water-miscible organic solvent is added to precipitate the desired organophosphate salts, and the final precipitate is washed to remove chloride salts and dried.
2. Description of the Prior Art
U.S. Pat. No. 4,647,672 represents a significant breakthrough in the art and describes stable, 2-polyphosphorylated species of L-ascorbic acid and its stereoisomers. The 2-polyphosphate ester of L-ascorbate described in this patent has proven to be an excellent source of vitamin C, particularly in aquatic feeds. It is furthermore believed that compounds of this type may have significant utility in human foods and pharmacological preparations.
The subject patent describes preparation of ascorbate 2-polyphosphate in liquid form, i.e., in aqueous solution. Such solutions contain significant amounts of inorganic contaminants which render them less suitable in human foods or other contexts requiring high vitamin potency or purity The '672 Patent discloses a conventional separation and purification technique for obtaining a dry product, involving use of ion exchange column chromatography. While this method does result in a dried, purified product, it is unsuitable for large-scale commercial preparation of a dried, powder-like product. The cost and technical difficulties associated with ion exchange column chromatography of polyphosphorylated L-ascorbate are formidable, and this method has not even been attempted on a commercial scale, even though the advantages of a dried, concentrated product are manifest.
There is accordingly a real and unsatisfied need in the art for an improved, low cost method for the purification and separation of salts of ascorbate 2-polyphosphate from aqueous solution which meets the twin goals of providing a dried, concentrated, powder-like product by means adapted for large-scale commercial production.